Generating random passwords is easy. All you need is some combination that's not in the dictionary and is quite long. If someone's got a rainbow table for all passwords up to 20 characters long, then you're stuffed whatever you do - and however well generated it is. Otherwise it doesn't really matter, within reason.
Personally I'm unlikely to remember total randomness (or even an approximation of it). But a short, non-grammatical phrase with random capitalisation, the odd special character and words spelt wrong, mis-ordered and interrupted should be good enough.